Actually, $26,000. (It's 2009 now.) If parents are married and kids are married, we could probably go up to $52,000. But, since the loan is above 10K (and above 100K so the rules minimizing the amount of imputed interest don't apply), Code Section 7872 and the regs at 1.7872 would apply and interest would be imputed as income to the lender.